1. Field of Use
This invention relates generally to mobile and stationary industrial vacuum loaders having bag house filtration systems for the collection of dust escaping from material being sucked into the hopper and, in particular, to means for removing collected dust from the bag house and returning it to the hopper.
2. Description of the Prior Art
Industrial vacuum loaders are used to load particulate or granular material from piles, bins, trucks, railroad cars, ship holds, or the like into a hopper for transport or conveyance to another location. Such loaders may be mobile and mounted on railroad cars, truck bodies or other vehicles. Or, such loaders may be staionarily mounted in a fixed location in an industrial plant. Some such industrial vacuum loaders employ a large enclosed hopper into which the particulate or granular material such as iron ore, cement, bauxite, alumina or the like is drawn through a flexible laoding hose attached to the hopper inlet and means are provided to unload the hopper as by dumping or tilting. Low pressure for suction purposes is maintained in the hopper by means of a relatively large engine-driven positive displacement rotary blower which has its suction port connected to an air outlet port on the hopper and has its pressure port connected to atmosphere. To prevent dust, fines or other extremely small air-suspended particles in the material being loaded from being drawn from the hopper and through the blower for discharge to the atmosphere, dust filtration means in the form of an enclosed bag house is connected between the air outlet port in the hopper and the suction port on the blower. The bag house comprises an upper chamber wherein a filter in the form of a plurality of porous bags is disposed and a lower dust collection chamber located below the bags in which the filtered dust collects and from which the dust can be removed as required through a cleanout port. Dust-laden air drawn from an air outlet port in the hopper is introduced into the bag house through an intake port located near the lower ends of the bags, passes in a tortuous path between and through the porous bags, and exits in dust free condition from the bag house though an outlet port located near the upper ends of the bags.
An inherent problem with such vacuum loaders is that, when loading the hopper with dry or fine materials, the bag house can become completely filled up with collected dust before the hopper fills up. This interferes with proper operation of the loader and requires time-consuming and costly shutdown of the loader and cleanout of the bag house through the cleanout port though the hopper still has unused capacity. The larger the capacity of the hopper, the more chance there is for this to happen. Attempts have been made to alleviate this problem by providing small hoppers or chutes for the dust collection chamber at the bottom of the bag house and installing air locks and a small positive displacement blower to pneumatically blow the collected dust from the aforesaid small hoppers or chutes back into the hopper through a conveying hose. However, the pneumatic conveying hose in such an arrangement is, of necessity, relatively small in diameter to match the air-handling capacity of the small blower and plugs easily with dust of most materials thereby introducing further cleanout problems.